WARNING: The following contains major spoilers for “Crisis on Infinite Earths, Part 1,” which aired Sunday on The CW.

The CW's "Crisis on Infinite Earths" crossover has teased an insane number of cameos, only some of which were revealed through formal announcements and leaks. While the majority of the crossover's premiere episode, which aired Sunday, focused on the antimatter wave that threatened Supergirl's Earth-38, there was still room for guest appearances.

In fact, much of the opening sequence was devoted to cameos from DC properties. Following a voiceover from The Monitor that chronicled the birth of the multiverse and the Age of Heroes, the episode takes a detour through a parade of familiar faces.

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Earth-89, Alexander Knox

The first takes viewers to Earth-89, with Robert Wuhl reprising his role as Alexander Knox from 1989's Batman.

Knox was a reporter for the Gotham City Gazette who pestered police in director Tim Burton's film about reports of a six-foot-tall bat. He appears at the beginning of thr episode, reading a newspaper that trumpets the headline, "BATMAN CAPTURES JOKER." He looks over his shoulder at the Bat-Signal in the red skies, and says, "I hope you’re watching, big guy."

Earth-9, Robin and Hawk

The episode then shifts to Earth-9 San Francisco, home of DC Universe's Titans, whose potential appearance in the crossover was long subject of speculation. We get only a quick look at Robin (Curran Walters) and Hawk (Alan Ritchson), as there’s a flash of light. No lines, just confused looks toward the camera as Crisis hits their Earth.

Earth-X, The Ray

The Ray (Russell Tovey) was last seen in live-action two years ago in "Crisis on Earth-X," although he also appeared on CW Seed's animated Freedom Fighters: The Ray. He pops up only briefly in "Crisis," flying through the air as Earth-X is seemingly destroyed by the antimatter wave.

Earth-66, Dick Grayson

In contrast to the bleak places we’ve seen so far, Earth-66 is as bright and colorful as the 1966 Batman series. Burt Ward reprises his role as Dick Grayson, who walks his dog -- is that Ace, the Bat-Hound? -- as the sky becomes red. He turns around and yells, in true Robin fashion, “Holy crimson skies of death!”

It’s great to see that Dick keeps his love of big exclamations around, even if we don’t get the “Batman!” we expect at the end of it.

Earth-38, End-of-the-World Guy

Not an existing DC character, but this is a fun one, nonetheless. The first scene on Earth-38, where much of the episode takes place, features Wil Wheaton as a man on the street ranting about the end of the world, and proclaiming that Supergirl can’t save them. He’s mostly right - Crisis is here, the world is coming to an end, and Supergirl doesn’t save Earth-38. However, he's wrong in that Supergirl can at least save him -- from a dragon that appears in the middle of his rant.

Earth-16, Oliver Queen

Later in the episode, Lois Lane, Brainiac and Sara Lance search for Jonathan Kent, the infant son of Clark and Lois, whose rocket was detoured from the doomed Argo to another Earth, which turns out to be from the Star City 2046 episode of Season 1 of Legends of Tomorrow. Until now, there’s never been an indication the Legends visit different Earths. Given explanations from earlier this episode, and when the Multiverse was introduced in The Flash, however, it makes sense their time travel would involve, or inadvertently create, alternate Earths. There, they of course encounter that reality's Oliver Queen, meaning Stephen Amell pulls double duty in this episode.

And this is only the beginning. We still have four more episodes of "Crisis" to fit in more cameos in between the big, literally Earth-shattering storylines.

"Crisis On Infinite Earths" continues tonight at 8 ET/PT on Batwoman and Tuesday at 8 p.m. ET/PT The Flash. After the winter hiatus, the crossover will conclude Tuesday, Jan. 14, at 8 p.m. ET/PT on Arrow and at 9 p.m. ET/PT on DC's Legends of Tomorrow.

Next: Crisis Chapter One’s Biggest Surprise Is a Major, Unexpected Death